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IR absorption — Parallax Forums

IR absorption

Robert SchwartzRobert Schwartz Posts: 141
edited 2005-02-18 22:50 in General Discussion
Hey guys. I know that black matte surfaces absorb IR the best, but are there any other things that will affect how much a surface absorbs/reflects IR?

Comments

  • steve_bsteve_b Posts: 1,563
    edited 2005-02-18 01:06
    Glossy surfaces will reflect where rough surfaces will diffuse the light enough that i doesn't reflect back to the source/detector.

    If you have 'rough' surfaces coming in between your beam then having a larger dot will make it more likely you'll have enough light reflect back to your detector.

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    Steve
    http://members.rogers.com/steve.brady
    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-18 03:18
    Actually, I want the opposite. Im making a sumo-bot to compete next year. I am planning on painting it all matte black, but was wondering if there is any other ways of making it "ir invisible".
  • steve_bsteve_b Posts: 1,563
    edited 2005-02-18 03:34
    IR is just a different wavelength of light than 'visible' light.·
    So, if you wanted to make it IR invisible....then you wouldn't be able to find it! haha

    The best you can do is do the B2 stealth bomber thing and make all the angles sharp.
    There was a russian scientist that did all his math stuff and determined that a triangle is the best geometric shape that would be least visible to radar.
    Garbage trucks have a larger profile than a honda civic and not just because of the shear size....the truck has a flat profile that directs the pulse straight back, where the civic has a low profile and not as much signal is reflected.

    Can you Jam him?· Jamming him would jam yourself, if you use a similar sensor.
    If you've ever seen the side of a mountain that was avalanche prone...they put up large snow fences (but permanent).· These are kind of like baffles...they disrupt the force of the wave coming down the mountain.
    So, if you look on the exhaust ports of the B2, you'll see similar baffles...they let radar beams in but not out.

    BUT...having said all that....for you, it's not that the material is wood or metal, it's if it'll reflect light.
    Flat black is a good start.

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    ·

    Steve
    http://members.rogers.com/steve.brady
    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-18 03:55
    Thanks steve. I think my design is good, its basicly just a triangle wedge. I don't want to jam the opponents sensors, as thats not really a fair fight. I would prefer losing in a good fight than winning because I disabled the opponent. Anyways, I plan on using IR sensors too, so disabling them wouldn't even be an option. I there a way to also be sonar invisible?
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-18 07:54
    I believe the stealth bombers use a coating that is part iron/part carbon but it was designed for radio waves not ir.

    Just make your robot out of one huge silicon crystal: http://acept.la.asu.edu/PiN/rdg/irnuv/irnuv.shtml·devil.gif

    if you want to be scientific about it you can get an ir photography filter, bunch of paints, thin card stock and a thermometer. Paint the stock, place lens, thermometer, card stock in the sun for a period of time, take the measurement, repeat each day at the same time for each paint. The one that results in the highest temperature absorbs the most IR.

    If you dont want to go through the trouble, get flat black and mix in some graphite.

    Or cover your surfaces with mirrors if no panel is likely to be perpendicular to your opponent (slightly leaning them inward towards the top will accomplish this). The IR beam when reflected will be too high for the sensor to pick up. The more slanted the angle the smaller the "visibility" radius arround your robot will be.
  • achilles03achilles03 Posts: 247
    edited 2005-02-18 12:33
    IR invisible? By that, do you mean you're trying to prevent other robots from using rangefinding sensors on yours? I'm not sure how "dark" the material would have to be to work well, but if you find a good IR "blackbody", let me know. Some of the darkest astroids in space have relfectivities around 4%, and I don't think you'll be able to get much below that.

    One thing you might want to consider is putting a "mirrored cone" around your robot (minus the top), kind of like a moon crater in shape. When another robot tries to sense yours with IR, the IR will be reflected up away from the sensor, and not back. The stealth uses similar technology by having flat, diamond-like surfaces (most of the radar is reflected away from the source at odd angles, not back), unlike a typical aircraft which has rounded surfaces that have portions that are always aimed directly at the radar source.

    Hope that helps,
    Dave
  • steve_bsteve_b Posts: 1,563
    edited 2005-02-18 13:49
    Heck, maybe have an array of IR detectors on your bot and sense what direction the beam is coming from.· Then move a 'scatter' device to that sector and block their beam....OR, launch your weapons to that sector in hopes of disabling the detector.

    Remember when Voltron lost their shield abilities and then they went to site specific shields...where operators would turn on a small area that would deflect the·damage in that spot.· HAHA....sorry, was reaching there!

    If you're bot is a big wedge....then having a 'mirror-like' surface should be good enough to give you a low reflective profile.· paint your bot with your black paint....give it 3 or 4 good coats...then wet sand it with some fine grit sand paper.· This is what car painters do to give it that mirror look...it's not just a 'clear-coat'; otherwise you get an orange peel texture look.

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    ·

    Steve
    http://members.rogers.com/steve.brady
    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • MacGeek117MacGeek117 Posts: 747
    edited 2005-02-18 16:14
    Or you could just head over to Romulus and grab one of their cloaking devices. lol.gif
    bugg

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    I think I know what I'm doing...
    ...Maybe...

    Post Edited (bugg) : 2/18/2005 4:25:17 PM GMT
  • steve_bsteve_b Posts: 1,563
    edited 2005-02-18 17:53
    Or buy a IR transmitter that has a 'hotter' beam point and aim it at other targets.· Might have to use a lens....

    But basically you would send out a decoy to fool the other bot.· Of course, you would have this offset to your own detector so that it wouldn't pick it up.

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    ·

    Steve
    http://members.rogers.com/steve.brady
    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-18 21:17
    I'm not sure if a mirror would work, seeing how robots are going to be shoved on and off it. I guess I could find a cheap plastic one that I could use. Well, I can't really give you a definate yet on how well it will work. In about a year I can tell you how it performs in a real situation (sumo). Thanks guys.
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-18 21:44
    Then I would electroplate the panels either in silver or chrome. (silver would require a clear coat to prevent tarnishing)

    Post Edited (Paul Baker) : 2/18/2005 9:47:24 PM GMT
  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-18 22:28
    You can't electroplate things onto plastics can you?
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-02-18 22:35
    Yes but i believe it requires a special process (I think it must first be plated through a chemical process if im not mistaken)
  • Robert SchwartzRobert Schwartz Posts: 141
    edited 2005-02-18 22:50
    Sounds like more trouble than its worth. Im not really into playing with chemicals in my basement. [noparse]:)[/noparse]
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